Fluid motors typically receive a flow of pressurized fluid and convert the potential energy of the pressurized fluid into kinetic mechanical energy. Often, a fluid motor produces rotary motion configured to drive one or more operatively connected devices, e.g., gears or sprockets. A fluid pump is usually connected to the fluid motor to provide a substantially continuous flow of pressurized fluid to the fluid motor. The amount of mechanical energy output of a fluid motor is often varied by adjusting either the amount of flow and/or the pressure provided by the fluid pump, for example, by adjusting a stroke length of one or more pistons of the fluid pump or by restricting a pump provided constant flow and pressure via one or more valves disposed between the fluid pump and the fluid motor. These methods of adjusting the mechanical energy output of the fluid motor may undesirably waste energy by using only a portion of the delivered energy when adjusting the stroke length or by dissipating heat when restricting flow and pressure via the valves.
U.S. Pat. No. 6,651,545 (“the '545 patent”) issued to Nippert discloses a variable displacement fluid translating device. The device of the '545 patent includes a housing, a rotary cam having an eccentric cam surface, and a plurality of pistons disposed within a plurality of piston bores disposed radially with respect to the rotational axis of the rotary cam. The eccentric cam surface is in contact with the plurality of pistons and is configured to affect a reciprocal motion of the plurality of pistons relative to a respective piston bore. The plurality of piston bores are in fluid communication with a plurality of actuators and an inlet port and an outlet port. The device of the '545 patent operates as a fluid pump by driving the rotary cam forcing the plurality of pistons to reciprocate within the plurality of piston bores and force fluid therein to the inlet or outlet port. The device of the '545 patent also operates as a fluid motor by fluidly reciprocating the plurality of pistons within the plurality of piston bores to rotate the cam via the eccentric cam surface. The device of the '545 patent may selectively adjust the amount of fluid displaced when the device operates as a fluid pump by selectively adjusting one or more of the piston strokes via the plurality of fluid actuators.
The device of the '545 patent may be configured to operate as both a fluid pump and fluid motor, however, when operating as a fluid motor, the plurality of pistons may undesirably translate a relatively large reciprocating displacement thereof into a small rotary motion of the rotary cam. Additionally, the device of the '545 patent may include adjusting the amount of rotary motion by adjusting the amount of fluid displacement, however, increased range or degree of adjustability may be desirable.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.